CSS Tip: Mastering CSS Variables

Custom properties provide a powerful, flexible way to handle theming and dynamic styling.

here are some tips you should know :

Fallback Values for Robustness

CSS variables support fallback values, which can be a lifesaver in environments where variables may not be supported or where a variable isn’t defined yet

color: var(--primary-color, #000); /* If --primary-color isn't set, default to black */

Using JavaScript to Manipulate Variables

You can dynamically manipulate CSS variables in real-time using JavaScript. This is useful for creating interactive UI changes based on user actions

document.documentElement.style.setProperty('--primary-color', '#ff6347');

Using Variables in Media Queries

CSS variables work seamlessly with media queries, enabling responsive design adjustments without redundancy.

:root {
    --font-size-base: 18px;
    @media (min-width: 768px) {
        --font-size-base: 16px;
    }
}

p {
    font-size: var(--font-size-base);
}

Dynamic Theming with Variables

Switching between light and dark themes is easy by changing variables at the root level, without touching individual components

:root {
    --bg-color: #ffffff;
    --text-color: #333333;
}

/* Dark Theme */
[data-theme="dark"] {
    --bg-color: #1e1e1e;
    --text-color: #f5f5f5;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
}

Now you can use JavaScript to toggle themes by changing the data-theme attribute

document.documentElement.setAttribute('data-theme', 'dark');

Component-Level Overrides

CSS variables can be scoped to individual components for more granular control over styles.

:root {
    --shadow-color: gray;
}

button {
    box-shadow: .1em .1em .1em var(--shadow-color);
    &:hover {
        --shadow-color: skyblue;
    }
}